1. Technical Field
The present disclosure relates to pulse width modulation (PWM) dimming technologies, and more particularly, to a PWM dimming circuit.
2. Description of Related Art
Currently, there are mainly three kinds of dimming technologies: PWM dimming, analog dimming and digital dimming. Many light emitting diode (LED) drivers on the market can support one or more of the dimming technologies. The PWM dimming is a dimming technology that utilizes simple digital pulses to switch on and off a white-light LED driver repeatedly. By use of the PWM dimming technology, the output current can be changed by simply providing digital pulses of different widths so as to adjust brightness of the white-light LED.
In conventional LED driving circuits, a balance integrated circuit (IC) is usually used for PWM dimming or analog dimming. Specifically, brightness of the LED is adjusted by using an internal module of the balance IC to adjust a duty ratio of the output current. Usually, the balance IC has a very complex circuit and requires use of a corresponding dimming module in the balance IC. The dimming module mainly functions to multiply an input PWM signal with a driving signal of a MOSFET which is used for current balance so that the MOSFET switches on or off according to the PWM signal to make a duty ratio of the LED consistent with that of the PWM signal. In this way, the PWM dimming or analog dimming can be achieved. However, this adds to both difficulty in design of the circuit and the manufacturing cost.